Several examples of utilizing peritoneal (ascites) tumor growth to assess the activity of chemotherapeutics have been reported in the literature, including one that utilized LOX melanoma cells. For example, R. H. Shoemaker et al., Proc. Am. Assoc. Cancer Res., 26:330 (1985), reported that LOX melanoma cells could form ascites, and that the model could be used to assess cancer therapeutics by using a survival endpoint around day 20. In 2003, H. Nakanishi et al., Cancer Sci., 94:112-118 (2003), reported a peritoneal model utilizing gastric cancer cells tagged with GFP. This model was used to study the chemosensitivity of peritoneal cell growth to an anti-cancer agent. Tumor burden was measured by harvesting GFP cells from the peritoneal cavity, homogenizing the cells, centrifuging cells at 10000 g, and then measuring the fluorescence of the supernatant using a fluorescence counter. In order to extrapolate the number of cells that produced the fluorescence, a calibration curve was used with a standard number of GFP cells. In this model, >1 month was needed for ascites production in the peritoneum.
Several examples of utilizing metastatic tumor growth to assess the activity of chemotherapeutics have been reported in the literature. The LOX experimental metastasis model was reported by O. Fodstad et al., Int. J. Cancer, 41:442-449 (1988), by R. H. Shoemaker et al. in 1991, and by M. Yeng et al., Clin. Cancer Res., 5:3549-3559, (1999) with GFP-tagged cells.
For example, Fodstad et al. reported that LOX cells injected into the tail vein of immunocompromised mice were able to metastasize to lung with nearly 100% frequency. The size and number of colonies differed from one animal to another however, and thus the authors found it was not possible to establish an accurate relationship between the cell number injected and resulting colony number. For this reason, they used animal survival as an endpoint rather than counting metastatic colonies on the lungs.
In a report by R. H. Shoemaker et al. 1991, LOX-L cells were generated by 16 cycles of subcutaneous (sc) tumor transplantation, followed by removal of a lung metastasis for growth in vitro. Unlike the parental cell line LOX, the LOX-L cell line was able to metastasize to lung from sc tumor implantation, whereas LOX cells could only metastasize from iv implantation. LOX-L sc tumors were utilized to study the effects of chemotherapeutics on metastasis, however the authors went through the very arduous procedure of transplanting metastatic lungs into new mice for evaluation of pulmonary metastases. In subsequent studies (Wang X et al., Int. J. Cancer, 112:994-1002, 2004) the LOX-L model was implanted iv, however metastases were evaluated simply by counting colonies and utilizing a survival endpoint.
In a report by M. Yeng et al., Clin. Cancer Res., 5:3549-4559 (1999), metastasis models were established utilizing GFP tagged LOX or B16 melanoma cells. For the LOX-GFP model, tumors were implanted orthotopically (transdermally), whereas for B16 GFP model, cells were implanted iv. GFP was used to identify lung metastases, however the authors failed to quantify the lung metastatic tumor burden, and instead used a subjective (qualitative) endpoint. They simply visualized metastases in live animals or upon necropsy by utilizing a fluorescent microscope to establish the presence or absence of metastases.